Monitoring Faults

Vocabulary

Outline

Monitoring Faults (intro)

• Parkfield, California
  • every 22 years, town had earthquake between 1857-1966
  • scientist predicted strong earthquake between 1985-1993
    • nothing happened for a while
  • small medium sized earthquakes rumbled along San Andreas fault near Parkfield in 1993-1994.

Devices that Monitor Faults

• Earthquake detecting instruments
  • four scales
    • creep meter, laser-ranging devices, tiltmeter, satellite monitors
• Creep Meters
  • uses wire to detect horizontal movement
    • uses wire stretched across a fault
    • on one side wire is grounded to a past, the other end is attached to a weight that moves when the plate does
  • uses how much weight has moved to detect earthquake

  A picture of a Creep meter.

• Laser-Ranging Devices
  • uses a laser beam to detect any fault movement
    • calculates any change in the fault
• Tiltmeter
  • like a carpenter's level
    • detects vertical movement with two bulbs that have liquid in them
  • if liquid is out of place the fault has moved
• Satelite Monitor
  • makes images of faults to detect changes
    • bouces radio waves off the ground and back

Monitoring Risks in the USA

• Can't predict earthquakes well
  • can't tell when stress builds up
    • sometimes we know when stress builds up, but earthquakesdon't happen
• Where earthquakes are most common and dangerous
  • geologists locate where earthquakes occur where faults are active
  • risk of earthquakes is highest at Pacific Coast in California (home sweet home!), Washinton, and Alaska
    • that's is where Pacific and North American plates meet
  • earthquakes rare in the east